Field of the Invention
The present invention relates to a device for preventing separation of a belt from a motor pulley to drive a load through a belt. More particularly, it relates to an improvement in such device for preventing a belt from comming off from a pulley of a motor due to removal of a load at the time of non-operation of the motor.
The device of this type has been generally used in a clutch motor for driving a sewing machine because it has been necessary to frequently remove the sewing machine from a table or to incline it for the purpose of repair or adjustment of the machine.
Namely, the conventional device for preventing separation of the belt such as, for instance, in the West German Pat. No. 1760810 is constructed in such a manner that a protection cover is attached to a motor so as to cover one side of a pulley fixed to the output shaft of the motor, the protection cover being provided with a guide slot for permitting a bolt to pass therethrough and a belt separation preventing plate is attached to the protection cover by means of the bolt to prevent a V-belt wound on the motor pulley from comming off from the same. It is, therefore, necessary to move the belt separation preventing plate along the guide slot of the protection cover once the motor has been mounted in a position so that a space gap between the belt separation preventing plate and the outer peripheral surface of the V-belt in its stretching state has a predetermined dimension (generally, of about several millimeters) to prevent the V-belt from coming off the pulley due to its looseness when the sewing machine is removed from the table or inclined to the table for the purpose of repair or adjustment. Accordingly, it is desirous to perform an easy adjustment of the position of the belt separation preventing plate. In the conventional device, adjustment of the plate to fix it in a position has been carried out by fastening or releasing the bolt passing through the guide slot.
However, the conventional device has suffered such disadvantages that it has been necessary to use a spanner of the size which fits to the head of a bolt in order to fasten it to locate the belt separation preventing plate, with the consequence that a spanner for exclusive use is required as an accessory tool which has invited increasing of cost and furthermore, it has been difficult to carry out a fastening operation by using the spanner under the table.